ln a two-for-one twisting machine of the aforesaid type it is necessary to catch the yarn, which shoots upward between the feed package pot and the inner jacket of the balloon limiter as it is threaded, and to advance same to the other portions of the device, the yarn being generally guided through a yarn guide eyelet and over an overfeed roll to a traversing yarn guide, whence it advances to a takeup package, which is normally driven by a package drive roll.
With manually operated spindles, it is in general not difficult to catch the yarn at the upper end of the space between the feed package pot and balloon limiter with the hand, after having visually recognized its location on the circumference, and to continue the threading.
However, a partially or fully automated procedure in the operation of twisting spindles requires a positioned yarn. This positioning relates at least to a partial range of the entire circumference of the annular gap. Shortly above the balloon limiter, the threaded yarn is, for example, taken over by correpondingly formed suction nozzles. In order to make the mechanized threading procedure fully operable, it it necessary to separate the rotor of the twisting spindle from the drive, so that the channel outlet on the yarn storage disk corresponds with the suction nozzle arranged above the balloon limiter.
A two-for-one twisting machine of the initially described type is disclosed, for example, in German Patent DE-C-26 48 621. In this known machine, a yarn guide tube with a longitudinal slot is arranged above the annular gap between the upper edge of the protective pot and balloon limiter, into which tube the yarn is inserted by means of a suction current. Associated to this yarn guide tube are further means for advancing and transferring the yarn.
Other two-for-one twisting machines of this type are described, for example, in German Patent DE-C-20 65 140.
Further known are two-for-one twisting machines, in which the yarn exits from the spindle at a predetermined point of the spindle circumference above the balloon limiter without having to position the spindle rotor. Such a device is disclosed, for example, in German Patents DE-C-27 18 351 and DE-C-24 08 563. In these known devices, an annular molded body is arranged on the underside of the rotating plate of the twisting spindle, which defines, together with the rotating plate and the yarn storage disk, an annular chamber, which is provided with an outlet opening terminating in the gap between the feed package pot and balloon limiter. The surfaces of baffles arranged inside the molded body see to it that either the rotating plate is rotated thereby providing an additional positioning effect, or, however, that the yarn is guided directly to a predetermined position on the twisting spindle.
The hitherto known devices have turned out to be expensive and not adequately reliable in operation. It is necessary either to provide the required individual devices on each twisting spindle or to associate same with a handling device. However, also the latter has turned out to be constructionally expensive, inasmuch as it is necessary to combine in one device both the spindle positioning and the means for a positioned upward movement of the yarns to be threaded.